The federal government will not preclear a photo voter identification law signed by Texas governor Rick Perry because it would have a greater impact on Hispanic voters, a Justice Department official said in a letter to state authorities on Monday.

Hispanic registered voters in Texas were either 46.5% or 120% more likely than average voter to lack a form of photo ID, according to data the state submitted to DOJ. The first data set was sent in September and the second in January, though Texas has refused to tell federal authorities which they believe is more accurate.

The first data set said that 6.3% of Hispanic registered voters lacked photo ID compared to 4.3% of the general pool of registered voters, while the second data set said 10.8% of Hispanic registered voters lacked ID compared to 4.9% of registered voters.

"In conclusion, the state has not met its burden of proving that, when compared to the benchmark, the proposed requirement will not have a retrogressive effect, or that any specific features of the proposed law will prevent or mitigate that retrogression," DOJ assistant attorney general Thomas Perez wrote in a letter to state authorities.

"Additionally, the state has failed to demonstrate why it could not meet its stated goals of ensuring electoral integrity and deterring ineligible voters from voting in a manner that would have avoided this retrogressive effect."

Perez also wrote that Texas "has not provided an explanation" for the disparate results. "More significantly, it declined to offer an opinion on which of the two data sets is more accurate," he wrote.

Texas preemptively sued attorney general Eric Holder back in January for not preclearing the law in a timely manner. The Lone Star state claimed it did not collect racial and ethnic data on its citizens in an attempt to "facilitate a colorblind electoral process."

Texas had argued that DOJ had to let their law go into effect because the civil rights division precleared a similar Georgia voter ID law during the Bush administration. Georgia's law, however, was approved by political appointees over the objections of career staffers.

State officials first asked DOJ to preclear the law in July. DOJ followed up with a letter in September asking for more information on how the law would be implemented as well as a breakdown of how many of the 605,576 residents the state said do not have a Texas drivers license or photo ID card had Spanish surnames. Federal officials said in November that the data Texas provided wasn't adequate and Texas sued shortly after they submitted additional data on 12 January.